A conventional motor includes a breathing hole as a through hole for compensating pressure difference between an inside and an outside of the motor. For example, the motor includes a motor portion having a rotation shaft with a rotation axis and a speed reduction portion having a speed reduction means for reducing rotation speed of the rotation shaft. The motor portion and the speed reduction portion are connected to each other. The speed reduction means is accommodated in a gear housing, which includes a through hole for communicating between the inside and the outside of the motor. Preferably, the motor having this breathing hole has water proof construction in order to protect the motor from the water to penetrate into the motor through the breathing hole.
The water proof construction is disclosed in, for example, German patent application publication No. 3716912. In this motor, a positioning concavity for positioning a water proof sheet is formed on the surface of the gear housing. Further, the breathing hole extends from a center portion of the positioning concavity to the inside of the gear housing. The water proof sheet is arranged on the bottom of the positioning concavity. Then, a seal member is arranged on a periphery portion of the water proof sheet. After that, a pressure application member having elasticity is inserted into the positioning concavity. Thus, the water proof sheet is fixed on an opening of the breathing hole, which is disposed on an outer side of the motor, so that the water proof sheet prevents the water from penetrating into the motor.
However, when the water proof sheet is fixed to the breathing hole, the seal member as a sealing means and the pressure application member as a fixation means are additionally necessary. Thus, the number of parts of the motor becomes larger. Accordingly, a manufacturing process of the motor becomes complicated, and productivity of the motor is reduced.
It is required for the motor to form the water proof construction for the breathing hole without increasing the number of parts of the motor.